1. Field of the Invention
The present invention relates to a bag for packaging liquid formed using a film of plastic, comprising a leaktight chamber for the liquid and a pocket, adjacent to this chamber, in which a pipe for withdrawing the liquid is housed, means being provided to give access to the inside of the said pocket, an opening being formed through part of the wall of this pocket, adjacent to the said chamber, to allow the said withdrawing pipe to enter the said chamber in a leaktight fashion. This invention also relates to a method for the manufacture of bags and for packaging liquid continuously in these bags.
2. Description of the Prior Art
There has already been proposed, especially in WO 95/23742, a bag for packaging liquid comprising an incorporated valve for controlling the outlet of liquid and which can be manufactured continuously from a film of thermoplastic. It has been proposed that a drinking straw be associated with this bag to allow the liquid to be accessed through the valve that consists of a passage formed between two layers of film which normally touch and which open when the drinking straw is inserted. Thus, when the drinking straw is withdrawn at least partially from the passage that forms the valve, this passage closes back up and the liquid can no longer get out. The drawback with this system lies in the fact that by withdrawing the drinking straw, this straw makes liquid in the passage of the valve come out, gradually soiling the outside of the bag.
Clearly it is not easy to make an effective seal in this kind of bag, even less so when this bag is equipped with a valve of the aforementioned type. The edges of the passage delimiting the valve are made by welding together films of thermoplastic. Now, by welding these films together, the structure of the substance of the film is locally altered and the film becomes amorphous and loses some of its elasticity, so detracting from the quality of seal that can be formed. The use of an element added on to the inlet end of this valve-forming passage is also precluded. This clearly demonstrates the complexity of the problem to be solved, it being necessary for the solution to be appropriate to the very low cost price that can be tolerated for a bag of this type. Other problems associated with this design of bag, and the solutions to which are combined and re-used in the present invention, have already been provided by the inventor of the present invention and have been covered by other protections. These in particular include the question of incorporating a drinking straw into the bag, and the tamper-proofing of this bag for obvious health and safety reasons.
By contrast, the problems associated with sealing and with a certain method of manufacture and of packaging the liquid continuously had hitherto not yet been dealt with satisfactorily. One of these problems is associated with incorporating a drinking straw into a closed pocket of the packaging in a manufacturing process that uses a material in the form of continuous strip.